Conventionally, as a battery system which includes a plurality of flat secondary batteries, there has been provided a battery system which is manufactured by taking into account vibration resistance and impact resistance (see JP 2014-44884 A, for example). Such a battery system includes: a battery assembly formed by stacking a plurality of flat secondary batteries in a thickness direction; a pair of end plates disposed on both end surfaces of the battery assembly in a stacking direction; bind bars connected to the pair of end plates and fixing the flat secondary batteries in the stacking direction by applying pressure to the flat secondary batteries; and an intermediate reinforcing plate disposed between the flat secondary batteries which form the battery assembly and fixed to the bind bars.
In such a battery system, the end plates and the intermediate reinforcing plate fix the stacked flat secondary batteries in a pressurized state. That is, in the battery system, the battery assembly (flat secondary batteries) is fixed in a state where the battery assembly is positioned with reference to the intermediate reinforcing plate.
Such a battery system is mounted on an automobile or the like as a power source and hence, there has been a demand for reduction of a weight of the battery system. However, the battery system having the above-mentioned configuration includes the intermediate reinforcing plate and hence, the battery system has a large weight because of the presence of the intermediate reinforcing plate.